CH644572A5 - GLASS REFLECTING HEAT WITH A NEUTRAL APPEARANCE. - Google Patents

Description

The present invention relates to a glass reflecting heat, especially for window, having a neutral external appearance and comprising a transparent support, an interference layer disposed on the support and consisting of a dielectric material having a refractive index greater than 2 and a layer of heat reflecting gold placed on the interference layer on the side opposite to that of the transparent support.

For glazing buildings, more and more use is made of glazing which has good sun protection properties. For this purpose, the glazing must have a power of transmission of all of the solar radiation as low as possible while ensuring the best possible transmission of visible light. They must have at the same time an external appearance of neutral coloring and a reflective power similar to that of windows constituted by clear glass. In some cases, only • part of the building premises must be fitted with heat-reflective glazing (for example air-conditioned rooms for computers) while all other rooms are fitted with normal glazing glass, ie - say in clear glass. In these cases, it is desirable that the heat-reflecting glazing seen from the outside have the same visual reflection as the clear glass in order to ensure a harmony of the external appearance of the whole building. This is also the case for buildings which are fully equipped with heat-reflecting glazing, especially when these have to integrate harmoniously into their environment (for example in the case of tight urbanization in an old town).

The layers of gold have particularly established themselves as a coating for heat-reflecting glazing because they also have good sun protection properties for a transmission located in a range of less than about 50%. In fact, seen from the outside, these layers of gold are strongly tinted and are therefore not suitable for the aforementioned applications. It is true that, by reducing the thickness of the gold layer, it is also possible to obtain a neutral external appearance and a low visible reflection. However, the thickness of the layers which must be used is then such that one largely loses the properties of protection against the sun.

In this regard, the use of a heat-reflecting glazing of the type mentioned, in which an interference layer of a dielectric material having a refractive index greater than 2 is placed between the transparent support, generally consisting of a sheet silicate glass, and the gold layer, improves. Indeed, this two-layer system comprising an interference layer and a gold layer makes it possible to slightly extend the area of low neutral reflection in the visible to thicker gold layers, while ensuring better protection against the sun. However, this is still insufficient for most applications. In this way we obtain (by looking at the glazing from the side of the glass, therefore corresponding to the view from the outside when the glazing is placed) a reflection in the visible which still has just a neutral coloring when the gold layer has a thickness of 7 nm.

A heat-reflecting glazing of this type made of clear glass, having a layer of gold 7 nm thick and an interference layer with a high refractive index of zinc sulfide, placed between the glass support and the layer d ', has the following technical characteristics:

Transmission of solar radiation = 55%

Reflection of solar radiation

(measured from the glass side) = 13%

Light transmission (referred to

sensitivity of the human eye) = 66.3%

Reflection in the visible

(measured from the glass side) = 8.2%

This latter value corresponds entirely to the reflection rate of a sheet of clear glass (8%).

However, for many applications, it is necessary to lower the rate of transmission of solar radiation from heat-reflecting glazing of this kind. In most cases, effective protection against the sun requires transmission values of less than 50%. If, to do this, the thickness of the gold layer of the glazing reflecting the cha5 is increased

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them of the type indicated, it is no longer possible to obtain a neutral external appearance. Nor does one achieve the expected result by further modifying the thickness of the interference layer. In the thickness range of the interference layer which interests us, the increase in this thickness changes the impression of coloring from reddish violet to pale green without the transition range between these colors comprising a neutral coloring zone. .

Therefore, it is proposed - by the present invention - to modify the heat-reflecting glass of the type mentioned so that an increase in the thickness of the gold layer ensures transmission of solar radiation in the range below about 50%, while ensuring the maintenance of a neutral external appearance with regard to coloring.

The window according to the invention comprises a transparent support, an interference layer disposed on the support and constituted by a dielectric material having a refractive index greater than 2 and a layer of gold reflecting heat arranged on the interference layer. on the side opposite that of the transparent support. The desired result is obtained by using a gold layer having a thickness of between 7 and 10.5 nm and by placing on the gold layer, on the side opposite to that of the interference layer, a neutralization layer in chromium, iron, nickel, titanium, alloys of these metals or an alloy of chromium, aluminum and iron.

A particularly preferred embodiment of the invention provides that the neutralization layer consists of a chromium / nickel alloy containing 20% by weight of chromium and 80% by weight of nickel. Other preferred embodiments of the invention are given in the dependent claims. In this context, it has proved especially expedient for at least the neutralization layer, but preferably all the layers applied to the transparent support, to be produced by vacuum deposition. It is also advantageous to apply between the transparent support and the interference layer - which in this case consists of zinc sulfide - an intermediate dielectric layer, substantially devoid of absorbing power of visible light and acting as a layer adhesion, this intermediate layer consisting of a material whose refractive index corresponds substantially to that of the transparent support, as is known for example by the patent application published in the Federal Republic of Germany under the number DE-AS 2203943.

In the glazing according to the present invention, it is possible to have on the gold layer on the side opposite to that of the interference layer a neutralization layer which is preferably constituted by nickel, chromium, iron or titanium, or by an alloy of these metals or by an alloy of chromium, iron and aluminum. However, it is particularly advantageous to use, for example, chromium and nickel alloys such as those mentioned in the patent granted in the Federal Republic of Germany under the number DE-PS 2029181, where they are described as constituents of the absorbent layer.

Thanks to the presence of the neutralization layer according to the present invention, it is possible to obtain in the layer system: interference layer with a high refractive index - gold layer, for thicknesses of the gold layer greater than 7 nm, an appearance in reflection on the glass side completely neutral coloring (when used as window glazing, the heat-reflecting glazing is normally mounted so that the transparent support is placed on the outside of the building and the layers on the inside of the room). At the same time, the importance of reflection always corresponds well to that of a simple sheet of clear glass. The range of thicknesses of the gold layer in which this coloring neutrality effect occurs is limited to thicknesses of the gold layer up to 10.5 nm. With thicker layers of gold, it is no longer possible to obtain coloring neutrality by means of the neutralization layer, even if the thickness of the interference layer is adjusted.

It is particularly advantageous that, in the heat-reflecting glazing according to the invention, the coloring neutrality can be obtained by increasing the thickness of the gold layer at the same time. This increase in the thickness of the gold layer is advantageous for two reasons. First of all, due to the selective filtering properties of the gold layer (high transmission in the visible region of the spectrum for low transmission and high reflection in the near infrared), a light transmission / total transmission ratio is obtained. more advantageous solar radiation. It should also be added that the part absorbed by the glazing and the resulting heating are limited compared to a solution in which, for example, the transmission of solar radiation would only be lowered by the use of absorbent glass or absorbent layers. In addition, in the field of thermal radiation, that is to say for wavelengths greater than 4 μm, the increase in the thickness of the gold layer causes an increase in the reflectivity of the infrared on the side of the glazing bearing the layer system. Therefore, the heat exchange of the glazing with the interior of the room or with a second sheet of clear glass placed in the vicinity of the heat reflecting glazing according to the invention, on the side of the interior of the room (configuration of insulating glass) is further lowered, which improves the coefficient k of thermal insulation.

The fact that in the range of thicknesses of the gold layer from 7 to 10.5 nm it is possible to obtain coloring neutrality by means of the neutralization layer according to the invention constitutes a surprising result, because the layers of metal or alloys intended as neutralization layers have in the visible spectrum area an absorbing power practically independent of the wavelength, that is to say that they uniformly weaken the incident radiation. In addition, it is surprising that very small layer thicknesses of the order of 1 nm can already produce the color neutrality effect. For layers of this thickness, the absorption rates are still of the order of 10%, so that they do not cause an undesirable reduction in the transmission of the layer system nor therefore the light transmission thereof.

The synergistic effect obtained, according to the invention, by the combination of the neutralization layer and the increase in the thickness of the gold layer was not foreseeable for those skilled in the art. Thus, according to the patent granted in the Federal Republic of Germany under the number DE-PS 2029181, it was certainly known to use, between a sheet of glass and for example a layer of gold reflecting heat, an absorbent layer which the composition corresponds to that of the neutralization layer according to the present invention.

However, this document makes no allusion to the mode of action of the neutralization layer provided by the invention in combination with an interference layer, in particular a layer of zinc sulphide, placed on the other side of the layer d 'gold. In US Patent No. 3476594, a layer system is described comprising a transparent support, namely a glass sheet, successively coated with a layer of nickel and a layer of gold. This arrangement of layers does not correspond to that which is proposed by the present invention. According to this, a neutralization layer consisting for example of a chromium / nickel alloy is placed on a two-layer system constituted by an interference layer and by a gold layer arranged on the side opposite to the glass sheet. In the patent application published in the Federal Republic of Germany under the number DE-AS 1911036, it is a question of the use of layers of metal, semi-metal or metal alloy in connection with a system of interference. By way of example, a layer of gold is inserted between two interference layers, in ratios which differ completely from those of the heat-reflecting glazing according to the present invention. The patent granted in the South African Republic under No. 76.03269 relates, for its part, to obtaining a pink tone by the use of copper as a layer of heat-reflecting metal, this layer being covered by an additional layer of metal or alloy of a material corresponding to the neutralization layer of the present invention. However, this publication does not contain any indication that it

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It is possible to obtain a synergistic effect in the manner described using, as provided by the invention, a system comprising a neutralization layer combined with a layer of gold.

An exemplary embodiment of the invention will be described below in detail, with reference to the accompanying drawing. 5

The schematic drawing, which includes a single figure, shows in section an embodiment of a glazing reflecting heat according to the invention.

As can be seen in the figure, an interference layer 12 consisting of a dielectric material having a refractive index greater than 2 has been placed on a transparent support 10, namely a sheet of clear glass. which, in this exemplary embodiment, consists of zinc sulfide. A layer of gold 14 of a thickness chosen between 7 and 10.5 nm, reflecting heat, is applied thereto, and finally a neutralization layer 16 made of a chrome / nickel alloy comprising 80% nickel. and 20% chromium.

To manufacture the glazing shown in the drawing, the interference layer 12 was first sprayed with zinc sulfide under a pressure of 5 × 10 -5 Torr on a sheet of clear glass 4 mm thick, in an installation high vacuum deposition. The gold layer 14 was then successively vaporized to a thickness of 9.3 nm and the neutralization layer 16 to a thickness of 1.3 nm. The glazing thus obtained has the following properties: Transmission of solar radiation = 44%

Reflection of solar radiation 25

(measured on the glass side) = 18%

Light transmission

(related to the sensitivity of the human eye) = 57%

Reflection in the visible

(measured from the glass side) = 8.7%

Seen from the glass side, the glazing has a neutral appearance which practically corresponds, from an optical point of view, to that of a simple pane of clear uncoated glass.

A comparison of the technical data of the heat-reflecting glazing described above with that of a neutral-colored glazing comprising an interference layer and a gold layer 7 nm thick shows that the use of the d 'thicker gold in the glazing according to the invention significantly improves the selectivity, that is to say the light transmission / transmission of solar radiation. The improvement allows to go from 66.3 / 55 = 1.21 to 57/44 = 1.30. It should also be noted that the reflection of solar radiation goes from 13 to 18%. This means that, compared to other solutions in which the reduction of the transmission of solar radiation to less than 50% is obtained exclusively by absorption, the solar radiation heats the glazing according to the invention less strongly. Consequently, the risk of breakage by thermal shock is reduced. Another advantage of using a thicker gold layer is that, as a result of the higher reflection of the gold layer in the thermal radiation region (range of longer wavelengths) at 4 | im), the radiative exchange between the coated face and the interior of the room or a second glass sheet placed inward is also considerably reduced. As a result, the coefficient k of thermal insulation is greatly improved. Thus, the effective emission power in a direction perpendicular to the surface, which is 0.18 for a thickness of the gold layer of 7 nm, is lowered to about 0.11 in the example of a layer according to the invention.

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1 drawing sheet

Claims (17)

644,572 1: Heat reflecting glass, especially for window, having a neutral external appearance and comprising a transparent support, an interference layer disposed on the support and constituted by a dielectric material having a refractive index greater than 2 and a layer of gold reflecting heat placed on the interference layer on the side opposite to that of the transparent support, characterized in that the thickness of the gold layer (14) is between 7 and 10.5 nm and in that a neutralization layer of chromium, iron, nickel, titanium, alloys of these metals or an alloy of chromium, aluminum and iron is placed on the layer of gold (14) on the side opposite to that of the interference layer (12). 2. Glass according to claim 1, characterized in that the neutralization layer (16) consists of a chromium / nickel alloy containing 20% by weight of chromium and 80% by weight of nickel. 2 3. Glass according to one of claims 1 or 2, characterized in that the thickness of the neutralization layer (16) is at least 0.8 nm. 4. Glass according to claim 3, characterized in that the thickness of the neutralization layer (16) is less than 6 nm. 5. Glass according to claim 4, characterized in that the thickness of the neutralization layer (16) is approximately 1.3 nm. 6. Glass according to one of claims 1 to 5, characterized in that the thickness of the gold layer (14) is approximately 9.3 nm. 7. Glass according to one of claims 1 to 6, characterized in that the interference layer (12) consists of zinc sulfide. 8. Glass according to claim 7, characterized in that it comprises, between the transparent support (10) and the interference layer (12) of zinc sulfide, an intermediate dielectric layer devoid of light absorbing power visible, consisting of a material whose refractive index corresponds substantially to that of the transparent support. 9. Glass according to claim 8, characterized in that the intermediate layer consists of a metal oxide or a mixed oxide of metals. 10. Glass according to claim 9, characterized in that the intermediate layer consists of silicon oxide. 11. Glass according to claim 8, characterized in that the intermediate layer consists of a glass. 12. Glass according to one of claims 8 to 11, characterized in that the thickness of the intermediate layer is less than the wavelength of visible light. 13. Glass according to one of claims 1 to 12, characterized in that the transparent support (10) consists of a silicate glass. 14. A method of manufacturing the window according to claim 1, characterized in that at least the neutralization layer (16) is deposited under vacuum. 15. Method according to claim 14, characterized in that all the layers (12,14,16) applied to the transparent support (10) are deposited under vacuum. 16. Insulating glass comprising several panes, at least one of which, which is intended after mounting to be disposed towards the outside of the building, is constituted by a heat-reflecting glass according to one of claims 1 to 13, characterized in that the panes are arranged at a certain distance from each other. 17. Glazing according to claim 16, characterized in that the panes are glued to each other by adhesive sheets.